In recent years, power consumption by radio base stations (base transceiver station) has been increasing due in part to increase in scale of the radio base stations with increase in traffic volume in radio communication networks. For communication carriers, the increase in the power consumption by the radio base stations leads to increase in costs of maintenance and administration of their business and it is therefore desirable to reduce the power consumption by the radio base stations.
A technique using handover as follows has been known as a method of reducing the power consumption by the radio base stations. A radio base station includes a CFN generating unit configured to generate a connection frame number (CFN) that makes switching timing for hard hand over (HHO), in a call processing/maintenance processing monitor unit. When performing push out control over a call in communication, the call processing/maintenance processing monitor unit instructs the CFN generating unit to generate a CFN that makes uninterruptible HHO possible. The push out control refers to finding a new baseband resource that allows a call in communication in a relevant baseband resource to autonomously continue the communication and thereby causing the call to continue the communication by using the new resource. After receiving the instruction, the CFN generating unit generates the CFN and transfers the generated CFN information to the source baseband resource and the destination baseband resource. The source baseband resource and the destination baseband resource perform the push out control by determining timings to start and stop signal processing under the push out control based on the notified CFN.
Another technique using handover as follows has been known. When number of radio channels not in use in a radio base station is equal to or larger than a specified number and number of radio channels not in use in another radio base station which is included in control signals received from another radio base station is equal to or larger than the specified number, the former radio base station instructs a mobile station communicating with the radio base station to effect handover and brings about the handover of the mobile station to another radio base station. After verifying that the handover has normally been done, the former radio base station gradually weakens transmission power and enters into a sleep state.
There has been known another technique in which uplink is synchronized by performance of a contention-based random access procedure between a terminal (user equipment) and a base station with the terminal maintaining control resources when a time alignment timer is expired or is not operated.
There has been known another technique in which, upon transmission of common control channel (CCCH) SDU and buffer status reports (BSR) by a mobile terminal, radio resources allocated to the mobile terminal are initially allocated to the CCCH SDU and are thereafter allocated to the buffer status reports so that MAC PDU is generated and transmitted.
There has been known another technique in which a terminal stores time alignment information received from a base station in a buffer and maintains an operation of a time alignment timer which is currently running in a contention-based random access procedure and in which the terminal discards the time alignment information received from the base station in case where the terminal does not receive a contention resolution message from the base station before a contention resolution timer expires.
Japanese Laid-open Patent Publications Nos. 2004-80698 and 2003-37555 and Japanese National Publication of International Patent Applications Nos. 2011-520376, 2011-524713, and 2011-509019 are examples of related art.